Answers to Topic 7 Exercises

Exercise 1

1. a) C4H10 b) C4H8 c) C4H8

a) b) c)

(1 other possibility) (one other possibility) (two other possibilities)

2. a) alkane b) alkene c) bromoalkane

Exercise 2

1. a) 2,2-dimethylbutane b) 4-bromobut-1-ene c) but-2-ene d) chlorodimethylpropane e) methylpropane f) 1,2-dibromopropane

g) but-1-ene h) methylbut-2-ene

2. a) b) c)

d) e) f)

g) h)

Exercise 3

1.

1-chlorobutane 2-chlorobutane

2-chloromethylpropane 1-chloromethylpropane

2.

but-1-ene but-2-ene

methylpropene

3.

hexane

2-methylpentane 3-methylpentane

2,2-dimethylbutane 2,3-dimethylbutane

lowest boiling point: 2,2-dimethylbutane

2,3-dimethylbutane

3-methylpentane

2-methylpentane

highest boiling point: hexane

Exercise 4

1. a) mixtures of hydrocarbons with similar boiling points

b)

·  crude oil is passed into a fractionating column where it boils

·  the column is hotter at the bottom than at the top

·  the vapour rises up the column until it condenses

·  small hydrocarbons have weak van der Waal’s forces, hence low boiling points and condense near the top of the column

·  large hydrocarbons have strong van der Waal’s forces, hence high boiling points and condense near the base of the column

c) liquefied petroleum gas camping stoves, gas for cooking

gasoline fuel for cars

naphtha petrochemicals

kerosine fuel for aircraft

diesel fuel for lorries

lubricating oil lubrication

fuel oil fuel for ships

wax candles

tar road surfacing

d) the fractions all have different uses

mixed together they have no useful applications


2. a) thermal cracking: high temperature

high pressure

makes alkenes

catalytic cracking: high temperature

slight pressure

zeolite catalyst

makes motor fuels

makes aromatic hydrocarbons

b) it converts hydrocarbons for which supply exceeds demand

into hydrocarbons for which demand exceeds supply

3. a) C8H18 + 12½O2 à 8CO2 + 9H2O

b) C8H18 + 8½O2 à 8CO + 9H2O

C8H18 + 4½O2 à 8C + 9H2O

c) less energy released, CO is a toxic gas, C particulates are carcinogenic

4. a) CO2, CO, C, NO2 or NO, SO2, unburned hydrocarbons

b) CO2 greenhouse gas

CO reduces ability of blood to carry oxygen

C carcinogen

NO2 or NO cause acid rain/destruction of ozone layer

SO2 acid rain

unburned hydrocarbons greenhouse gases/photochemical smog

c) 2CO + 2NO à N2 + 2CO2